chore: import upstream snapshot with attribution

wrapper/monitoring/prometheus/README.md

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+# Prometheus Wrapper
+
+The `prometheus` wrapper package exposes standard request metrics (request
+count, latency, errors) for go-micro services and clients, so they can be
+scraped by a Prometheus server with zero extra boilerplate.
+
+Resolves [micro/go-micro#2893](https://github.com/micro/go-micro/issues/2893).
+
+## Installation
+
+```go
+import prom "go-micro.dev/v5/wrapper/monitoring/prometheus"
+```
+
+## Exported Metrics
+
+All metrics are labelled with `service`, `endpoint` and `status`
+(`"success"` or `"fail"`). Labels are kept small on purpose to avoid
+blowing up Prometheus memory.
+
+| Metric                          | Type      | Description                                 |
+|---------------------------------|-----------|---------------------------------------------|
+| `micro_request_total`           | Counter   | Total number of requests handled.           |
+| `micro_request_duration_seconds`| Histogram | Request latency distribution (seconds).     |
+
+The `micro` prefix can be overridden with `prom.ServiceName("myapp")`.
+
+## Basic Usage
+
+```go
+import (
+    "go-micro.dev/v5"
+    prom "go-micro.dev/v5/wrapper/monitoring/prometheus"
+)
+
+func main() {
+    service := micro.NewService(
+        micro.Name("example.service"),
+        micro.WrapHandler(prom.NewHandlerWrapper()),
+        micro.WrapClient(prom.NewClientWrapper()),
+        micro.WrapSubscriber(prom.NewSubscriberWrapper()),
+    )
+
+    service.Init()
+
+    if err := service.Run(); err != nil {
+        panic(err)
+    }
+}
+```
+
+To expose the metrics to Prometheus, serve the default `promhttp` handler
+on a side HTTP endpoint:
+
+```go
+import (
+    "net/http"
+
+    "github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+go func() {
+    http.Handle("/metrics", promhttp.Handler())
+    _ = http.ListenAndServe(":9100", nil)
+}()
+```
+
+Then point Prometheus at it:
+
+```yaml
+scrape_configs:
+  - job_name: 'example.service'
+    static_configs:
+      - targets: ['localhost:9100']
+```
+
+## Wrappers
+
+| Constructor               | Wraps                   | Notes                                      |
+|---------------------------|-------------------------|--------------------------------------------|
+| `NewHandlerWrapper`       | `server.HandlerWrapper` | Incoming RPC handlers.                     |
+| `NewSubscriberWrapper`    | `server.SubscriberWrapper` | Event subscribers (uses topic as endpoint). |
+| `NewCallWrapper`          | `client.CallWrapper`    | Outgoing unary RPC calls only.             |
+| `NewClientWrapper`        | `client.Wrapper`        | Outgoing `Call` **and** `Publish`.         |
+
+`NewClientWrapper` is the right choice when you want metrics for both
+`Call` and `Publish`; use `NewCallWrapper` if you only care about unary
+calls and want lower overhead.
+
+## Configuration
+
+All constructors accept functional options:
+
+```go
+prom.NewHandlerWrapper(
+    prom.ServiceName("myapp"),                          // metric name prefix
+    prom.Namespace("prod"),                             // Prometheus namespace
+    prom.Subsystem("api"),                              // Prometheus subsystem
+    prom.ConstLabels(prometheus.Labels{"dc": "eu-1"}),  // labels on every metric
+    prom.Buckets([]float64{0.005, 0.05, 0.5, 1, 5}),    // latency buckets
+    prom.Registerer(myRegistry),                        // custom registerer
+)
+```
+
+Defaults:
+
+- `ServiceName`: `"micro"`
+- `Buckets`: `prometheus.DefBuckets`
+- `Registerer`: `prometheus.DefaultRegisterer`
+
+## Reusing Collectors
+
+Creating multiple wrappers with the same options (e.g. `NewHandlerWrapper`
+and `NewClientWrapper` together) is safe: the collectors are cached per
+`(name, namespace, subsystem)` triple and `AlreadyRegisteredError` from
+Prometheus is handled transparently, so the existing collector is reused.
+
+## Testing
+
+The package ships with unit tests that use a fresh `prometheus.Registry`
+per test to keep assertions isolated:
+
+```bash
+go test ./wrapper/monitoring/prometheus/...
+```
+
+## License
+
+Apache 2.0